title: Expression of floral identity genes in Clianthus maximus during mass inflorescence abortion and floral development.
abstract: OBJECTIVE
  Clianthus maximus is a leguminous perennial with an unusual order of floral organ insertion, and inflorescences produced year round that nearly all abort except during a limited time in autumn. This study aimed to determine at what point in floral organ differentiation abortion occurred and whether the expression of the floral identity genes underlies this cessation in flower development.
  
  
  METHODS
  Inflorescences were harvested across an annual cycle and flower development was examined by light and scanning electron microscopy. Expression of the C. maximus-equivalents of LEAFY (LFY), APETALA1 (AP1), PISTILLATA (PI) and AGAMOUS (AG) was monitored simultaneously by quantitative, reverse transcriptase PCR.
  
  
  RESULTS
  Only those inflorescences formed in autumn proceeded to anthesis. Organogenesis had not begun in inflorescences that aborted. The C. maximus-equivalents of AP1, PI and AG were expressed in sepals, petals, carpels and stamens, as expected from the ABC model of floral organ identity specification; furthermore, the order of expression of the three genes reflected the unusual pattern of organ differentiation. Low expression of LFY and AP1 was observed during inflorescence abortion.
  
  
  CONCLUSIONS
  Predictions of gene expression based on the ABC model were upheld despite the unusual mass abortion of inflorescences and the non-standard pattern of organ formation. The lack of expression of LFY and AP1 in inflorescences may have been the cause of inflorescence abortion.
authors.affiliation: School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
authors.forename: Jiancheng
authors.initials: J
authors.lastname: Song
authors.forename: John
authors.initials: J
authors.lastname: Clemens
authors.forename: Paula E
authors.initials: PE
authors.lastname: Jameson
mesh_terms: D001483:Base Sequence; D007887:Fabaceae / Q000235:genetics* / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D056626:Inflorescence / Q000235:genetics* / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure; D026161:MADS Domain Proteins / Q000235:genetics / Q000378:metabolism; D018519:Meristem / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009154:Mutation; D009928:Organ Specificity / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D026161:MADS Domain Proteins; D010940:Plant Proteins; D014157:Transcription Factors